During autumn 1984, at a location in central Ontario, a study of the elemental composition of aerosols and precipitation was undertaken to determine the feasibility of making daily multielemental measurements on a routine basin, to probe the potential for gaining insight into pollutant origin from multielemental composition, and to estimate trace element deposition to an acid-sensitive watershed. The concentrations of Ti, Br, Mn, In, Na, V, Al, Ca, Se, As, Sb, Pb, Fe, Mg, Cu, Zn, and Cd in aerosol and of Pb, Mg, Ca, As, Br, I, Mn, and V in precipitation were measurable routinely, using neutron activation, X ray fluorescence, and plasma emission spectroscopy. Standard high volume samplers for total aerosols below 15-μm diameter as well as dichotomous samplers and Anderson impactors for size fractionation were operated simultaneously with two wet-only precipitation collectors. Aerosol data revealed four components: one soil (Mg--Ti--Al--Ca--Fe) and three anthropogenic (Se--Sb--Pb--Cd--Br; Mass--Cu-So4=; In--As). Ranked in order of increasing mass fraction in 2.1- to 10-μm diameter particles are the elements Pb, S, Se, Br, As, Cl, Na, V, In, Cu, Mn, Al, Ba, Ti, Ca.

A comparison of air parcel origin on high- and low-concentration days, using 3-day back trajectories, revealed major source regions of SO4=, Pb, In, As and Al. The element In is an excellent tracer of smelter emissions to the north. Although the estimated mean ratio of In/Se smelter emissions from central Ontario is close to that used in the regional aerosol approtionment model of Rahn and Lowenthal, its variability is greater than they propose. In 21 precipitation events, strong correlations were found between H+--SO4=, Ca++--Mg++, NO3---NH4+-Cl---V, and Pb--Br. The mass ratio of Br/Pb was higher in precipitation (0.47) than in aerosols (0.27), possibly omission estimated dry-deposited fraction of total deposition of Br, Pb, Mg, Mn, Ca, S, V, and As ranged from 10 to 42%. ¿ American Geophysical Union 1988